In recent years hydro-machining methods, including water jet cutting, have undergone significant advances. The reasons are obvious. A high pressure liquid jet, such as a water jet, can cut through several types of materials quite easily and it can be even programmed, through a computer software, to cut intricate patterns. Hydro-machining methods have been also used extensively in cutting patterns in various industries, such as the garment industry, the corrugated carton manufacturing industry, aircraft industries, electronics industry, and so on. Additional list of the application of hydro-machining is provided on page 91-95 of Wet Grit, Abrasive Waterjets, American Machinist, October 1989, Penton Publishing, Inc., Cleveland, Ohio, pages 84-97, incorporated herein by reference. For a general summary of various hydro-machining methods including water jet cutting methods, reference is made to the aforementioned special report on Wet Grit, Abrasive Waterjets, and to Guha, J., High-Pressure waterjet Cutting: An Introduction, Ceramic Bulletin, Vol. 69, No.6, 1990, pages 1027-1029, both incorporated herein by reference.
One of the major difficulties encountered in the hydro-machining technology is the short life span of the water jet mixing tubes used in the hydro-machining devices. The presence of abrasive particles in the water jets used in the hydro-machining devices reduces the life span of these mixing tubes due to abrasion. However, the life span of these mixing tubes can be significantly extended by producing them from diamond. Diamond is an allotrope of carbon exhibiting a crystallographic network comprising exclusively of covalently bonded, aliphatic sp.sup.3 hybridized carbon atoms arranged tetrahedrally with a uniform distance of 1.545 .ANG. between atoms and it is extremely hard, having a Mohs hardness of 10.
A method directed to improving the abrasion resistance of the annular interior surface of an annulus has been disclosed. Such a method comprises chemical vapor depositing abrasion resistant materials, such as diamond on the annular interior surface, which is placed in compression by virtue of the difference in the coefficients of thermal expansion between the annulus material and the CVD deposited diamond layer. However, the aforementioned method is not suitable to producing crack resistant articles having high L/D ratios (about 50) because it is difficult to chemically vapor deposit diamond along the annular interior surfaces of articles having high L/D ratios. By way of example, it is difficult to deposit diamond on the interior wall of an article of a funnel shape having a small diameter stem of about 0.500 millimeter outer diameter and having a long stem length of about 75 millimeters. The present invention is directed to addressing the problem of making such crack resistant funnel shaped articles having high L/D ratios.